1. Field of the Invention
The present invention generally relates to powered panel moving systems and, more particularly, to a powered panel moving system having electronic function circuitry integrated with electronic motor drive circuitry for providing additional functionality beyond driving a motor for movement of a panel.
2. Background Art
Standard automotive power window systems employ a brush type direct current (DC) motor with reduction gearing and suitable rotary-to-linear motion transformation fixtures to enable the motor to raise and lower a window. The requirement to drive the window completely into a compressible weather seal upon closing and withdraw the window upon opening can lead to forces driving the window having a magnitude of many Newtons (N).
Suitable fixtures for converting motor torque into the required closure force include cable systems, worm gears, planetary gears, and rack and pinion gearing systems, and the like. A typical fixture uses a gear system such as planetary gears to convert an approximately 3,000 rpm motor speed at approximately 0.4 Nm torque to an output rotation of 120 rpm at 10 Nm for a 3000/120=25:1 torque multiplication and speed reduction. The 120 rpm output is then converted to linear motion to drive a window with near stall forces of up to 450 N or more and unobstructed speeds of up to 11 inch/sec or more.
Unfortunately, a force having a magnitude of more than 100 N is sufficient to cause injury when a human body part become entrapped in a window being closed by this force. Techniques used to prevent such injury include placing a sensor in the closure region of the window such as described in U.S. Pat. No. 6,782,759. This has the disadvantage of requiring the sensor.
Another common approach is to monitor for either motor stall current or a rapid rise in motor current caused by the window hitting an obstruction. The motor is then reversed. However, reversal on motor current sensing allows a significant fraction of the window closure force to be applied to the obstruction if the obstruction is a soft object such as a child's neck. Soft obstructions can be sensed via motor current sensing if motor speed and/or window position are also measured as described in U.S. Pat. No. 6,064,165. This has the disadvantage of requiring additional speed and/or window position sensors.
It is well known to those skilled in the art of employing electric motors that the torque developed by a DC motor is generally a function of its size and the current it draws. The power of a DC motor is a function of the drive voltage, number of armature turns, and the applied current. A primary design trade that is made in motor applications is in motor size. For comparable input drive voltages and currents, a larger DC motor produces more torque than a smaller DC motor. However, a smaller DC motor can have approximately the same rated power as a larger DC motor for approximately the same input voltage and current, but will have it at a higher speed and lower torque. A smaller motor also has less surface area and mass. This can result in higher temperature operation for a smaller motor running at the same drive voltage and power of a larger motor. As much of the heating is caused by I2 R losses in the armature winding, a way to mitigate this problem is to use a smaller gauge wire and add windings and then operate at a higher voltage. However, many DC applications such as automotive applications have limitations in drive voltage. This causes all motor choices to work within a fixed drive voltage.
A second design trade is in terms of DC motor type. Conventional brush type DC motors have an armature wound on a rotor of the motor. This can limit the power rating of the motor as the armature can dissipate heat from the load current only through its shaft and bearings and heat rejection to air inside the motor case. In an alternative design, most commonly used on DC brush-less motors, the armature winding is moved to the stator with the rotor equipped with permanent magnets. This has the advantage of allowing the armature windings to be heat sunk directly to the motor frame. Then within the limitations of the heat sink provided to the motor frame, the motor can in some cases be run at higher currents than a comparable sized motor with internal armature windings.
A smaller motor offers a primary advantage in terms of the cost of its materials and the reduced weight and volume it takes up within a system it is powering. However, the design choice of a smaller motor has disadvantages. To match the power output of a larger motor, a smaller motor operates at higher speed. This offers at least four design challenges.
The first design challenge is that higher speed operation reduces the useful life of any brushes that are used. The second design challenge is that a more extreme “gear reduction”/“mechanical advantage” ratio is required to recover the equivalent torque that would be obtained from a larger motor at the same power rating. For instance, a motor operating at 3,000 rpm with 0.4 Nm torque requires a 25:1 gear ratio to get to a target 120 rpm at 10 Nm. However, a smaller 30,000 rpm motor with 0.04 Nm torque requires a 250:1 reduction gear ratio to match to the same target 120 rpm at 10 Nm. This could cause more wear and acoustic emissions than experienced with the lower gear ratio operating at lower motor speed. The third design challenge is that human hearing sensitivity is lower at the 50 Hz of a 3,000 rpm motor than at the 500 Hz of a 30,000 pm motor, resulting in the higher speed motor presenting a higher audio profile than would a larger, slower motor.
The fourth design challenge is in matching the motor to the mechanical coupling means used to match the motor's mechanical output to whatever component the motor is intended to move, e.g., an automotive power window or panel. Motors can be mounted on and move with the component or can be mounted to the structure on which the component moves. Gearing can be used to provide mechanical advantage such as in the employment of planetary gears and even gearbox transmissions as described in U.S. Pat. No. 6,515,399. Often gearing is used in combination with levers such as in the “arm and sector” configuration commonly used in automotive power window applications and described in U.S. Pat. No. 6,288,464 or in a rack and pinion configuration.
Flexible drive components such as cables (described in U.S. Pat. No. 4,186,524), tapes (described in U.S. Pat. No. 4,672,771), chains, and belts can be employed as well. In systems with the motor on the movable component, a worm gear, toothed track or slotted track, can be mounted on the stationary structure and be used to drive the motor and the component through the desired range of motion. Additionally, the motors can be applied to pumps to drive pneumatic or hydraulic pistons to affect the desired component motion. Clutches as described in U.S. Pat. No. 6,288,464 and brakes as described in U.S. Pat. No. 6,320,335 can be employed in combination with the mechanisms here described to engage or disengage torques and forces and/or to lock motion.
In the case of power windows and panels, the motor and mechanical coupling can be used to affect a linear or rotational sliding motion of the subject component or can be used to drive a hinged motion. Other motion types and mechanical coupling means are possible.
The problem of brush wear can be addressed by using a brush-less DC motor design. However, this introduces more cost via the additional electronics required for brush-less operation.